If you have a large scene, viewing it through Camera View may not display all of the Objects in the scene.
One possibility may be that the clipping distance of the camera is too low.
The camera will only show objects that fall within the clipping range.

Sometimes when navigating you may be trying to zoom in but it seems that you have hit a limit
to how far you can zoom.
This is because Blender uses a central point to orbit around.

In practice this is good for modeling an object which you rotate about a lot to see from all sides
(think of a potter using a wheel).
However, this makes it awkward to explore a scene or model an object from the „inside“, for example.